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Top Forums Shell Programming and Scripting Sourcing Env file with eval works with ksh but not BASH Post 302954042 by waavman on Thursday 3rd of September 2015 05:46:26 PM
Old 09-03-2015
Hi Corona,

Yes you are right. I just didnot communicate right. What I meant was that Linux supports setuid bit for C/C++ binaries / Perl scripts. It doesnot support it for Java programs or shell scripts.
So my idea is to remove read permission on the /tmp/envfile.txt for rest of world. One common user will be owner of the perl script and the envfile.txt.
So when any of the 50 users other than the owner will not be able to read the envfile.txt which has confidential information but they will be able to run the shell scripts and source it inside the shell scripts using the eval command because when eval runs, the perl script it will run as the owner and be able to read the hidden envfile.txt.

The example I have given for this discussion forum is just a dummy example. In reality we have around 300 shell scripts which source the envfile.txt and which several users other than the owner will run. With the sudo solution you provided, there would be two complexities:
(1) Each of the 50 users' userids' should be given sudo access to run the shell scripts as the owner id
(2) Sudo access has to be given to each of those 50 userids' to run each of the 300 scripts as the ownerid

This could get very cumbersome.
I agree that somebody can notice the eval "`/tmp/filereader.pl /tmp/envfile.txt`" command
within the shell scripts and be smart enough to run it from command line to view the envfile contents.
But at least it is slightly difficult than running a straight 'vi envfile.txt' that even beginners to UNIX OS are familiar

thanks
 

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CHECKBASHISMS(1)					      General Commands Manual						  CHECKBASHISMS(1)

NAME
checkbashisms - check for bashisms in /bin/sh scripts SYNOPSIS
checkbashisms script ... checkbashisms --help|--version DESCRIPTION
checkbashisms, based on one of the checks from the lintian system, performs basic checks on /bin/sh shell scripts for the possible presence of bashisms. It takes the names of the shell scripts on the command line, and outputs warnings if possible bashisms are detected. Note that the definition of a bashism in this context roughly equates to "a shell feature that is not required to be supported by POSIX"; this means that some issues flagged may be permitted under optional sections of POSIX, such as XSI or User Portability. In cases where POSIX and Debian Policy disagree, checkbashisms by default allows extensions permitted by Policy but may also provide options for stricter checking. OPTIONS
--help, -h Show a summary of options. --newline, -n Check for "echo -n" usage (non POSIX but required by Debian Policy 10.4.) --posix, -p Check for issues which are non POSIX but required to be supported by Debian Policy 10.4 (implies -n). --force, -f Force each script to be checked, even if it would normally not be (for instance, it has a bash or non POSIX shell shebang or appears to be a shell wrapper). --extra, -x Highlight lines which, whilst they do not contain bashisms, may be useful in determining whether a particular issue is a false posi- tive which may be ignored. For example, the use of "$BASH_ENV" may be preceded by checking whether "$BASH" is set. --version, -v Show version and copyright information. EXIT VALUES
The exit value will be 0 if no possible bashisms or other problems were detected. Otherwise it will be the sum of the following error val- ues: 1 A possible bashism was detected. 2 A file was skipped for some reason, for example, because it was unreadable or not found. The warning message will give details. SEE ALSO
lintian(1). AUTHOR
checkbashisms was originally written as a shell script by Yann Dirson <dirson@debian.org> and rewritten in Perl with many more features by Julian Gilbey <jdg@debian.org>. DEBIAN
Debian Utilities CHECKBASHISMS(1)
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